X-ray microbeam diffraction in a crystal

Using the formalism of dynamical scattering of spatially restricted X-ray fields, the diffraction of a microbeam in a crystal with boundary functions for the incident and reflected amplitudes was studied in the case of geometrical optics and the Fresnel approximation (FA). It is shown that, for a wide front of the X-ray field, the angular distributions of the scattered intensity in the geometrical optics approximation (GOA) and the FA are approximately the same. On the other hand, it is established that, for a narrow exit slit in the diffraction scheme, it is always necessary to take into account the X-ray diffraction at the slit edges. Reciprocal-space maps and the distribution of the diffraction intensity of the microbeam inside the crystal were calculated.

Схема VLS-монохроматора высокого разрешения для синхротронного излучения

A high-resolution monochromator with a broad spectral range of 125 – 4200 Angstrem is designed for the measuring beamline for the projected synchrotron radiation source "SKIF" (Novosibirsk). The optical configuration of the monochromator comprises a grazing-incidence concave mirror, a plane VLS grating, and an exit slit. It is planned to use two replaceable VLS gratings with central line frequencies of 600 mm-1 and 150 mm-1 intended for subranges of 125 – 1000 Angstrem and 900 – 4200 Angstrem , respectively. Wavelength tuning in each of the two subranges is effected by only the rotation of the VLS-gratings. Due to the proper choice of p_1 VLS-grating coefficients, the focal distance varies only slightly over the entire spectral range, and the p_2 VLS-grating coefficients are used to suppress the aberrations of the mirror and the gratings. The resolving power of the configuration obtained by numerical ray tracing exceeds 1000 in the 125 – 1000 Angstrem range and 2000 in the 900 – 4200 Angstrem range.

New leaf-mine fossil from the Geumgwangdong Formation, Pohang Basin, South Korea, associates pygmy moths (Lepidoptera, Nepticulidae) with beech trees (Fagaceae,Fagus) in the Miocene

A nepticulid leaf-mine ichnofossil,Stigmellites janggiSohn and Nam, n. ichnosp., is described on the basis of a fossil leaf ofFagusfrom the early Miocene Geumgwangdong Formation in Pohang Basin. This mine trace is characterized by a linear-blotch type with a clear centric frass trail composed of closely and randomly dispersed pellets filling the mine width in the early stage. We found traces of a possible egg case and an exit slit from the leaf. These features are most consistent with those produced by members of Nepticulidae. Our record demonstrates for the first time the trophic association of Nepticulidae withFagusin the Miocene and suggests the persistence of a long-term association between the insect family and the plant genus from the Miocene to the present. Other Nepticulidae leaf mines in the Miocene and leaf-mine fossils from the Geumgwangdong Formation are briefly reviewed.UUID:http://zoobank.org/fff951f6-ca82-4cca-a274-863e0d91acaa

Analysis of effective pore pressure in asphalt pavement based on computational fluid dynamics calculation

A micromechanical model was established based on the fluid dynamics theory. This model could be used to calculate several kinds of data when the asphalt pavement under the influence of traffic loading is in water-saturated condition. The results showed that the maximum pressure inside the effective pore was located at the junction between exit slits and the pore wall. There was a positive correlation between the pressure and the vehicle speed. Therefore, the repeated traffic loading could cause emulsification, shift and even peeling of the asphalt membrane. Moreover, the bigger size of the exit slit is, the higher velocity of the fluid has. The high velocity flow keeps scouring both the exit slit and the lower boundary of pore wall. It will cause a bigger slit. Pressure distribution inside the effective pore is related to the number of the exit slit which connect with the pore. More exit slits means bigger pressure inside the effective pore. In addition, if asphalt membranes at exit slits have micro-cracking, the cumulative damage could appear easily and asphalt membranes could be peeled easily. Finally, a test was conducted so as to obtain the bonding strength and adhesion strength between asphalt and aggregate. Then, we can get accurate damage form and position during the scour process by comparing the numerical simulation results with experiment results.

Effect of X-ray spot size on liquid jet photoelectron spectroscopy

A 30 µm pinhole is introduced in the intermediate focus of the SIM beamline at the Swiss Light Source to improve the spot size at the second downstream focus, which is used here for liquid jet X-ray photoelectron spectroscopy experiments. The 30 µm pinhole reduces the beam dimensions from 250 (v) × 100 (h) µm to 75 × 45 µm for a vertical exit slit of 100 µm. The smaller X-ray spot results in a substantial decrease in the gas-phase contribution of the spectra from 40% down to 20% and will help to simplify the interpretation and peak assignments of future experiments.

Design of an ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline

A new ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline has been designed and is under construction at the Shanghai Synchrotron Radiation Facility. The beamline has two branches: one dedicated to angle-resolved photoemission spectroscopy (ARPES) and the other to photoelectron emission microscopy (PEEM). The two branches share the same plane-grating monochromator, which is equipped with four variable-line-spacing gratings and covers the 20–2000 eV energy range. Two elliptically polarized undulators are employed to provide photons with variable polarization, linear in every inclination and circular. The expected energy resolution is approximately 10 meV at 1000 eV with a flux of more than 3 × 1010 photons s−1at the ARPES sample positions. The refocusing of both branches is based on Kirkpatrick–Baez pairs. The expected spot sizes when using a 10 µm exit slit are 15 µm × 5 µm (horizontal × vertical FWHM) at the ARPES station and 10 µm × 5 µm (horizontal × vertical FWHM) at the PEEM station. The use of plane optical elements upstream of the exit slit, a variable-line-spacing grating and a pre-mirror in the monochromator that allows the influence of the thermal deformation to be eliminated are essential for achieving the ultrahigh-energy resolution.

Concepts for flexible and efficient monochromatization of X-rays by refraction to a relative bandwidth of the order of 0.5%

Recently it was shown experimentally that regular arrays of tiny prisms can be used as X-ray monochromators providing a spectral bandwidth of below 2%. Successively the measured spectral transmission functions of monochromators operated under different conditions were found to be in agreement with expectations within an analytical model. This type of monochromator focuses chromatically and thus necessitates the use of an exit slit for the monochromatization. This contribution will show that the lower limit for the achievable bandpass can be predicted under practically feasible experimental conditions. Refractive monochromators based on prism arrays are found to be feasible solutions for monochromatization with high transmission to a spectral bandwidth of the order of 0.5%. The bandwidth can easily be increased by adjusting the exit slit setting accordingly. Consequently, the presented refractive devices would make for tunable monochromators with tunable bandwidth, which provides more flexibility for an intermediate bandwidth of <1%, which multilayer monochromators have difficulty providing routinely.

Design of a high-flux and high-resolution VUV bending-magnet beamline

A high-flux and high-resolution VUV beamline (4–40 eV) has been designed and is under construction at SRRC. This beamline, which collects 50 mrad of horizontal radiation, uses a 6 m cylindrical-grating monochromator with an incident angle of 70° instead of the conventional normal-incidence-monochromator (NIM) design. Special features, such as movable entrance slit, bendable vertical focusing mirror and movable curved exit slit, are employed to enhance greatly the beamline performance. With both slit openings set at 10 µm, the energy-resolving power can reach as high as 70000. Photon fluxes of 1 × 1013 and 1 × 1010 photons s−1 are calculated for energy-resolving powers of 1000 and 40000, respectively. The best image size at the sample position is smaller than 0.45 × 0.2 mm.

Design of an 18 m spherical-grating monochromator at UVSOR

An 18 m spherical-grating monochromator with high resolution and high photon flux has been developed at the bending-magnet beamline BL2B2 of the UVSOR facility in the Institute for Molecular Science. The monochromator is designed to cover the energy range 20–200 eV by using three gratings: G1 (2400 lines mm−1, R = 18 m) at 80–200 eV; G2 (1200 lines mm−1, R = 18 m) at 40–100 eV; G3 (2400 lines mm−1, R = 9.25 m) at 20–50 eV. A resolving power of 5000 and a photon flux of more than 1010 photons s−1 are expected at a 100 mA ring current. A small including angle of 140° is adopted for G3 and two plane mirrors coated with aluminium are located between G3 and the exit slit as optical filters. These geometrical devices may contribute significantly to the reduction of the high-order lights.